It is of course common for machines to have aligned cylindrical bearing surfaces upon which its operating components are mounted. For example, in the automatic screw machines provided by Davenport Machine Tool Co., Inc., of Rochester, N.Y., the so-called "revolving" and "stationary" heads are aligned in such a coaxial relationship. Although being pinned against rotation after initial alignment, the stationary head is supported on a semi-cylindrical bearing surface that is coaxial with the bearing surface of the frame in which the revolving head is journalled.
To correct for wear during use, it is common practice to rebuild the revolving head frame opening of such a machine, to enable reboring to size. It is of course imperative that a precise coaxial relationship with the saddle bearing surface be established for the newly bored head frame surface, and that has heretofore been most difficult to achieve.